PPV is absolutely something that's tracked. In fact, if you read the instructions for use (equivalent to "package insert") for lab diagnostics, you'll find the

PPV is absolutely something that's tracked. In fact, if you read the instructions for use (equivalent to "package insert") for lab diagnostics, you'll find the manufacturer's truth tables and can calculate the PPV if it's not in there. FDA keeps them online, so you don't even need to buy the diagnostic. Look the up.